Method of making carbolic acid.



WEED STAIME PATENT OFJEIQE.

HERBERT H. DOW, 0F MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN.

METHOD OF MAKING CARBOLIC ACID.

No Drawing.

To all whom it may concern Be it known that I, HERBERT H. Dow, a citizen of the United States, and a resident of Midland, county of Midland, and State of Michigan, have invented a new and useful Improvement in Methods of Making Carbolic Acid, of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

The present improved process relates more particularly to the synthetic production of carbolic acid, or phenol, in contradistinction to its recovery from the co-called carbolic oil fraction of coal tar.

It has been generally accepted heretofore that the phenols cannot be prepared from the halogen derivatives of bcnzol, e. from chloro-, bromo-, or iodo-benzene, in the same way as the alcohols from alkyl chlorids, bromids or iodids, the halogen being bound too firmly to the benzene nucleus. On the other hand, if nitro -groups are present in proper position, an exchange of this kind can be effected by heating with aqueous sodium or potassium hydroxide, and the same is true of benzene-sulfonic acid, the resulting alkaline phenate in either case be ing readily converted into phenol by any acid, even by a very weak acid, like carbon dioxid in water.

I have found, however, that mono-brombenzol (C H Br), contrary to the accepted view, based on experience with mono-chlorbenzol, will react with dilute caustic soda under conditions of temperature and pressure easily attainable in commercial practice. Such reaction results not only in the production of the sodium phenate desired for use in order to convert the same into phenol, but the bromin present in the benzene compound is recovered in the form of sodium bromid, which is a valuable commercial product, so that there is no loss of bromin, except, of course, the small amount that inevitably disappears in all chemical reactions carried out on a commercial scale.

The present invention accordingly consists of the steps and means hereinafter fully described and particularly pointed out in the claims, the specific improvement disclosed Specification of Letters Patent.

Patented Aug. 6, 1918.

Application filed July 10, 1916. Serial No. 108,293.

constituting but one of various ways in which the principle of the invention may be used. I

As already indicated in the present process I utilize mono-brom-benzol by treating the same witlrdilute caustic soda under a temperature that will produce approximately 300 pounds pressure. Under such conditions of temperature and pressure, the following reaction will proceed in a satisfactory manner, viz:

The resulting sodium phenate is then converted into carbolic acid, or phenol, in the fashion already familiar to chemists as stated above, viz by treating the same with any suitable acid, even a weak acid such as that formed by a solution of carbon dioxid effecting the desired transformation, as illustrated by the following reaction, viz:

The sodium bromid resulting from the first reaction given above is a valuable prodnot in itself, and so no additional expense, but rather the contrary, is involved in using the bromin substitution product of benzol. Furthermore, the operative conditions with respect to temperature and pressure are readily maintainable and the process described has henceproved a very satisfactory one for the synthetic production of car bolic acid, which on account of its purity is not only excellently suited for pharmaceutical purposes, but has to be used in various industries 0. g. picric and salicylic acids, since the cresol's found as impurities in tar phenol are very undesirable in such industrial use and are practically impossible to eliminate entirely.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the folin the manufacture of hromo-derivative of benzene with an alkaline hydroxid solution, whereby the phenate of such alkali is produced; and then adding an acid to such phenate, whereby the latter is converted into phenol.

2. In a method of making phenol synthetically, the steps Which consist in treating mono-brombenzol With an alkaline hydroxid solution, whereby the phenate and bromid of such alkali are produced; and

then adding an acid to such phenate, Wherehy the latter is converted into phenol.

3. In a method of making phenol synthetically, the steps Which consist in treating mono brom-benzol with a dilute solution of sodium hydroxid, whereby sodium phenate and sodium bromid are produced; and then adding an acid to such phenate, whereby the latter is converted into phenol.

4c. In a method of making phenol synthetically, the steps Which consist in heating a mixture of mono-brom-benzol and a dilute solution of sodium hydroxid to a temperature producing a pressure of approximately 300 p0unds,.Whereby sodium phenate and bromid are produced; and then adding an acid to such phenate, whereby the latter ,is

converted into phenol. I

Signed by me, this 7th day of July, 1916.

HERBERT DOW. Attested by A. N. PATRIARCHE, JNo. F. OBERLIN. 

